Showing papers on "Routing (electronic design automation) published in 2012"

Synchronization in Vehicle Routing---A Survey of VRPs with Multiple Synchronization Constraints

Abstract: This paper presents a survey of vehicle routing problems with multiple synchronization constraints. These problems exhibit, in addition to the usual task covering constraints, further synchronization requirements between the vehicles, concerning spatial, temporal, and load aspects. They constitute an emerging field in vehicle routing research and are becoming a “hot” topic. The contribution of the paper is threefold: (i) It presents a classification of different types of synchronization. (ii) It discusses the central issues related to the exact and heuristic solution of such problems. (iii) It comprehensively reviews pertinent literature with respect to applications as well as successful solution approaches, and it identifies promising algorithmic avenues.

Joint VM placement and routing for data center traffic engineering

Abstract: Today's data centers need efficient traffic management to improve resource utilization in their networks In this work, we study a joint tenant (eg, server or virtual machine) placement and routing problem to minimize traffic costs These two complementary degrees of freedom—placement and routing—are mutually-dependent, however, are often optimized separately in today's data centers Leveraging and expanding the technique of Markov approximation, we propose an efficient online algorithm in a dynamic environment under changing traffic loads The algorithm requires a very small number of virtual machine migrations and is easy to implement in practice Performance evaluation that employs the real data center traffic traces under a spectrum of elephant and mice flows, demonstrates a consistent and significant improvement over the benchmark achieved by common heuristics

Exact Routing in Large Road Networks Using Contraction Hierarchies

Abstract: Contraction hierarchies are a simple approach for fast routing in road networks. Our algorithm calculates exact shortest paths and handles road networks of whole continents. During a preprocessing step, we exploit the inherent hierarchical structure of road networks by adding shortcut edges. A subsequent modified bidirectional Dijkstra algorithm can then find a shortest path in a fraction of a millisecond, visiting only a few hundred nodes. This small search space makes it suitable to implement it on a mobile device. We present a mobile implementation that also handles changes in the road network, like traffic jams, and that allows instantaneous routing without noticeable delay for the user. Also, an algorithm to calculate large distance tables is currently the fastest if based on contraction hierarchies.

Routing Protocols in Wireless Sensor Networks: A Survey

Abstract: Extensive usage of wireless sensor network (WSN) is the reason of development of many routing protocols. Recent advances in WSN now witness the increased interest in the potential use in applications like Military, Environmental, Health (Scanning), Space Exploration, Vehicular Movement, Mechanical stress levels on attached objects, disaster management, combat field reconnaissance etc. Sensors are expected to be remotely deployed in unattended environments. Routing as one key technologies of wireless sensor network has now become a hot research because the applications of WSN is everywhere, it is impossible that there is a routing protocol suitable for all applications. In this paper, the various routing protocol are classified and described. The growing interest in WSN and the continual emergence of new architectural techniques inspired surveying the characteristics, applications and communication protocols for such a technical area.

Cluster based wireless sensor network routing using artificial bee colony algorithm

Abstract: Due to recent advances in wireless communication technologies, there has been a rapid growth in wireless sensor networks research during the past few decades. Many novel architectures, protocols, algorithms, and applications have been proposed and implemented. The efficiency of these networks is highly dependent on routing protocols directly affecting the network life-time. Clustering is one of the most popular techniques preferred in routing operations. In this paper, a novel energy efficient clustering mechanism, based on artificial bee colony algorithm, is presented to prolong the network life-time. Artificial bee colony algorithm, simulating the intelligent foraging behavior of honey bee swarms, has been successfully used in clustering techniques. The performance of the proposed approach is compared with protocols based on LEACH and particle swarm optimization, which are studied in several routing applications. The results of the experiments show that the artificial bee colony algorithm based clustering can successfully be applied to WSN routing protocols.

The VTR project: architecture and CAD for FPGAs from verilog to routing

Abstract: To facilitate the development of future FPGA architectures and CAD tools -- both embedded programmable fabrics and pure-play FPGAs -- there is a need for a large scale, publicly available software suite that can synthesize circuits into easily-described hypothetical FPGA architectures. These circuits should be captured at the HDL level, or higher, and pass through logical and physical synthesis. Such a tool must provide detailed modelling of area, performance and energy to enable architecture exploration. As software flows themselves evolve to permit design capture at ever higher levels of abstraction, this downstream full-implementation flow will always be required. This paper describes the current status and new release of an ongoing effort to create such a flow - the 'Verilog to Routing' (VTR) project, which is a broad collaboration of researchers. There are three core tools: ODIN II for Verilog Elaboration and front-end hard-block synthesis, ABC for logic synthesis, and VPR for physical synthesis and analysis. ODIN II now has a simulation capability to help verify that its output is correct, as well as specialized synthesis at the elaboration step for multipliers and memories. ABC is used to optimize the 'soft' logic of the FPGA. The VPR-based packing, placement and routing is now fully timing-driven (the previous release was not) and includes new capability to target complex logic blocks. In addition we have added a set of four large benchmark circuits to a suite of previously-released Verilog HDL circuits. Finally, we illustrate the use of the new flow by using it to help architect a floating-point unit in an FPGA, and contrast it with a prior, much longer effort that was required to do the same thing.

A Stable Network-Aware VM Placement for Cloud Systems

Abstract: Virtual Machine (VM) placement has to carefully consider the aggregated resource consumption of co-located VMs in order to obey service level agreements at lower possible cost. In this paper, we focus on satisfying the traffic demands of the VMs in addition to CPU and memory requirements. This is a much more complex problem both due to its quadratic nature (being the communication between a pair of VMs) and since it involves many factors beyond the physical host, like the network topologies and the routing scheme. Moreover, traffic patterns may vary over time and predicting the resulting effect on the actual available bandwidth between hosts within the data center is extremely difficult. We address this problem by trying to allocate a placement that not only satisfies the predicted communication demand but is also resilient to demand time-variations. This gives rise to a new optimization problem that we call the Min Cut Ratio-aware VM Placement (MCRVMP). The general MCRVMP problem is NP-Hard, hence, we introduce several heuristics to solve it in reasonable time. We present extensive experimental results, associated with both placement computation and run-time performance under time-varying traffic demands, to show that our heuristics provide good results (compared to the optimal solution) for medium size data centers.

Design and Implementation of TARF: A Trust-Aware Routing Framework for WSNs

Abstract: The multihop routing in wireless sensor networks (WSNs) offers little protection against identity deception through replaying routing information. An adversary can exploit this defect to launch various harmful or even devastating attacks against the routing protocols, including sinkhole attacks, wormhole attacks, and Sybil attacks. The situation is further aggravated by mobile and harsh network conditions. Traditional cryptographic techniques or efforts at developing trust-aware routing protocols do not effectively address this severe problem. To secure the WSNs against adversaries misdirecting the multihop routing, we have designed and implemented TARF, a robust trust-aware routing framework for dynamic WSNs. Without tight time synchronization or known geographic information, TARF provides trustworthy and energy-efficient route. Most importantly, TARF proves effective against those harmful attacks developed out of identity deception; the resilience of TARF is verified through extensive evaluation with both simulation and empirical experiments on large-scale WSNs under various scenarios including mobile and RF-shielding network conditions. Further, we have implemented a low-overhead TARF module in TinyOS; as demonstrated, this implementation can be incorporated into existing routing protocols with the least effort. Based on TARF, we also demonstrated a proof-of-concept mobile target detection application that functions well against an antidetection mechanism.

Modeling the routing and spectrum allocation problem for flexgrid optical networks

Abstract: Flexgrid optical networks are attracting huge interest due to their higher spectrum efficiency and flexibility in comparison with traditional wavelength switched optical networks based on the wavelength division multiplexing technology. To properly analyze, design, plan, and operate flexible and elastic networks, efficient methods are required for the routing and spectrum allocation (RSA) problem. Specifically, the allocated spectral resources must be, in absence of spectrum converters, the same along the links in the route (the continuity constraint) and contiguous in the spectrum (the contiguity constraint). In light of the fact that the contiguity constraint adds huge complexity to the RSA problem, we introduce the concept of channels for the representation of contiguous spectral resources. In this paper, we show that the use of a pre-computed set of channels allows considerably reducing the problem complexity. In our study, we address an off-line RSA problem in which enough spectrum needs to be allocated for each demand of a given traffic matrix. To this end, we present novel integer lineal programming (ILP) formulations of RSA that are based on the assignment of channels. The evaluation results reveal that the proposed approach allows solving the RSA problem much more efficiently than previously proposed ILP-based methods and it can be applied even for realistic problem instances, contrary to previous ILP formulations.

Consistency in multi-vehicle inventory-routing

Abstract: Inventory-routing problems (IRPs) arise in vendor-managed inventory systems. They require jointly solving a vehicle routing problem and an inventory management problem. Whereas the solutions they yield tend to benefit the vendor and customers, solving IRPs solely based on cost considerations may lead to inconveniences to both parties. These are related to the fleet size and vehicle load, to the frequency of the deliveries, and to the quantities delivered. In order to alleviate these problems, we introduce the concept of consistency in IRP solutions, thus increasing quality of service. We formulate the multi-vehicle IRP, with and without consistency requirements, as mixed integer linear programs, and we propose a matheuristic for their solution. This heuristic applies an adaptive large neighborhood search scheme in which some subproblems are solved exactly. The proposed algorithm generates solutions offering a good compromise between cost and quality. We analyze the effect of different inventory policies, routing decisions and delivery sizes.

Ultralow-loss, high-density SOI optical waveguide routing for macrochip interconnects

Abstract: We report optical waveguides up to one meter long with 0.026 dB/cm loss fabricated in a 300nm thick SOI CMOS process. Combined with tight bends and compact interlayer grating couplers, we demonstrate a complete toolbox for ultralow-loss, high-density waveguide routing for macrochip interconnects.

Multicast Routing for Decentralized Control of Cyber Physical Systems with an Application in Smart Grid

Abstract: In cyber physical systems, communication is needed for conveying sensor observations to controllers; thus, the design of the communication sub-system is of key importance for the stabilization of system dynamics In this paper, multicast routing is studied for networking of decentralized sensors and controllers The challenges of uncertain destinations and multiple routing modes, which are significantly different from traditional data networks, are addressed by employing the theories of hybrid systems and linear matrix inequalities, thus forming a novel framework for studying the communication sub-system in cyber physical systems Both cases of neglible delay and non-negligible delay are discussed The proposed framework is then applied in the context of voltage control in smart grid Numerical simulations using a 4-bus power grid model show that the proposed framework and algorithm can effectively stabilize cyber physical systems

Cargo routing and empty container repositioning in multiple shipping service routes

Abstract: This paper considers the problem of joint cargo routing and empty container repositioning at the operational level for a shipping network with multiple service routes, multiple deployed vessels and multiple regular voyages. The objective is to minimize the total relevant costs in the planning horizon including: container lifting on/off costs at ports, customer demand backlog costs, the demurrage (or waiting) costs at the transhipment ports for temporarily storing laden containers, the empty container inventory costs at ports, and the empty container transportation costs. The laden container routing from the original port to the destination port is limited with at most three service routes. Two solution methods are proposed to solve the optimization problem. The first is a two-stage shortest-path based integer programming method, which combines a cargo routing algorithm with an integer programming of the dynamic system. The second is a two-stage heuristic-rules based integer programming method, which combines an integer programming of the static system with a heuristic implementation algorithm in dynamic system. The two solution methods are applied to two case studies with 30 different scenarios and compared with a practical policy. The results show that two solution methods perform substantially better than the practical policy. The shortest-path based method is preferable for relatively small-scale problems as it yields slightly better solution than the heuristic-rules based method. However, the heuristic-rules based method has advantages in its applicability to large-scale realistic systems while producing good performance, to which the shortest-path based method may be computationally inapplicable. Moreover, the heuristic-rules based method can also be applied to stochastic situations because its second stage is rule-based and dynamical.

Dynamic routing and spectrum assignment in spectrum-flexible transparent optical networks

Abstract: The continual growth of Internet traffic necessitates a high-capacity transmission platform and also highlights the importance of a multi-granularity transport network due to the flexible bitrates of Internet traffic. To meet these challenges, a spectrum-flexible optical network based on orthogonal frequency-division multiplexing (OFDM) transmission technologies has been proposed as a promising solution because of its large transport capacity and bandwidth flexibility. In spectrum-flexible optical networks, we focus on the complete dynamic routing and spectrum assignment (RSA) problem, which integrates the signal format selection subproblem, the routing subproblem, and the spectrum assignment subproblem. In the complete RSA problem, we jointly consider the spectrum continuity constraints, the transmission distance constraints, and the relationship between the traffic bitrate and the signal bandwidth. A nonlinear programing model is presented to state the complete RSA problem. To solve the problem, we introduce a decomposition approach that divides the nonlinear problem into three steps: selecting the modulation format, solving the linear basic RSA problem, and checking the transmission distances. Based on the decomposition, we propose two heuristic approaches: modulation level fixed and adaptive RSA approaches for the complete RSA problem. Through analysis of the approaches, we prove that, in theory, the modulation level adaptive RSA approach can find the optimal solution to the complete RSA problem. The two approaches are implemented and compared in simulations. The results prove that the modulation level adaptive approaches achieve a lower capacity blocking probability than the modulation level fixed approaches.

Routing Strategies Based on Macroscopic Fundamental Diagram

Abstract: An excess number of vehicles in a traffic network will reduce traffic performance. This reduction can be avoided by traffic management. In particular, traffic can be routed such that the bottlenecks are not oversaturated. The macroscopic fundamental diagram provides the relation between the number of vehicles and the network performance. One can apply traffic control on this level, in order to overcome computational complexity of network-wide control using traditional control levels of links or vehicles. Main questions in the paper are: (1) how effective is traffic control using aggregate variables compared to using full information and (2) does the shape of the macroscopic fundamental diagram change under traffic control. A grid network with periodic boundary conditions is used as example, and is split up into several subnetworks. The following routing strategies are compared: (1) the shortest path in distance, (2) the path shortest in time (dynamic due to congestion), (3) an approximation of the path shortest in time, but calculated using only variables aggregated for over a subnetwork, (4) an approximation of the path shortest in time, but calculated using only subnetwork accumulation. For routing strategy 3 and 4 only information aggregated over the subnetwork is used. The results show improved traffic flow using detailed information. Effective control is also possible using aggregated information, but only with the right choice of a subnetwork macroscopic fundamental diagram. Furthermore, when optimizing with detailed information – an hence in a subnetwork – the macroscopic fundamental diagram changes.

The time dependent vehicle routing problem with time windows: Benchmark problems, an efficient solution algorithm, and solution characteristics

Abstract: An algorithm that can tackle time dependent vehicle routing problems with hard or soft time windows without any alteration in its structure is presented. Analytical and experimental results indicate that average computational time increases proportionally to the number of customers squared. New replicable test problems that capture the typical speed variations of congested urban settings are proposed. Solution quality, time window perturbations, and computational time results are discussed as well as a method to study the impact of perturbations by problem type. The algorithm efficiency and simplicity is well suited for urban areas where fast running times may be required.

Zig zag routing

Abstract: Messages in a wireless multi-hop network comprising two or more rows of nodes are routed from a source node to a destination node along a path which zig-zags between a first row of nodes and a second row of nodes.

Lifetime Enhancement in Wireless Sensor Networks Using Fuzzy Approach and A-Star Algorithm

Abstract: Wireless sensor networks (WSNs) are used in many applications to gather sensitive information which is then forwarded to an analysis center. Resource limitations have to be taken into account when designing a WSN infrastructure. Unbalanced energy consumption is an inherent problem in WSNs, characterized by multihop routing and a many-to-one traffic pattern. This uneven energy dissipation can significantly reduce network lifetime. This paper proposes a new routing method for WSNs to extend network lifetime using a combination of a fuzzy approach and an A-star algorithm. The proposal is to determine an optimal routing path from the source to the destination by favoring the highest remaining battery power, minimum number of hops, and minimum traffic loads. To demonstrate the effectiveness of the proposed method in terms of balancing energy consumption and maximization of network lifetime, we compare our approach with the A-star search algorithm and fuzzy approach using the same routing criteria in two different topographical areas. Simulation results demonstrate that the network lifetime achieved by the proposed method could be increased by nearly 25% more than that obtained by the A-star algorithm and by nearly 20% more than that obtained by the fuzzy approach.

Approximating Congestion + Dilation in Networks via "Quality of Routing” Games

Abstract: A classic optimization problem in network routing is to minimize C + D, where C is the maximum edge congestion and D is the maximum path length (also known as dilation). The problem of computing the optimal C* + D* is NP-complete even when either C* or D* is a small constant. We study routing games in general networks where each player i selfishly selects a path that minimizes Ci + Di the sum of congestion and dilation of the player's path. We first show that there are instances of this game without Nash equilibria. We then turn to the related quality of routing (QoR) games which always have Nash equilibria. QoR games represent networks with a small number of service classes where paths in different classes do not interfere with each other (with frequency or time division multiplexing). QoR games have O(log4 n) price of anarchy when either C* or D* is a constant. Thus, Nash equilibria of QoR games give poly-log approximations to hard optimization problems.

An OSPF-Integrated Routing Strategy for QoS-Aware Energy Saving in IP Backbone Networks

Abstract: This paper deals with an energy saving routing solution, called Energy Saving IP Routing (ESIR), to be applied in an IP network. ESIR operation is integrated with Open Shorthest Path First (OSPF) protocol and allows the selection of the links to be switched off so that the negative effects of the IP topology reconfiguration procedures are avoided. The basic mechanisms which ESIR is based on are the concepts of SPT exportation and move. These mechanisms allow to share a Shortest Path Tree (SPT) between neighbor routers, so that the overall set of active network links can be reduced. Properties of moves are defined and the energy saving problem in an IP network is formulated as the problem of finding the Maximum Set of Compatible Moves (MSCM). The MSCM problem is investigated in two steps: firstly, a relaxed version of the problem, named basic MSCM problem, is considered in which QoS requirements are neglected; in the second step, the solution of the full problem, named QoS-aware MSCM problem, is faced. We prove that the basic MSCM problem can be formulated as the well-known Maximum Clique Problem in a graph; instead the QoS-aware MSCM introduces a condition equivalent to the Knapsack problem. ILP formulations to solve both the problems are given and heuristics to solve them in practical cases are proposed. The performance evaluation shows that in a real ISP network scenario ESIR is able to switch off up to 30% of network links by exploiting over-provisioning adopted by operators in the network resource planning phase and typical daily traffic trend.

Technique for communication in a communications network with routing by name

Abstract: A method and routing device are provided for aggregating of requests relating to a data segment of a stream into another request and for storing data segments belonging to different streams in a queue prior to the device routing them to client entities that have requested them. The method includes: determining a credit associated with a stream, the credit varying based on a number of requests transmitted by client entities and relating to data segments belonging to the stream; and, on receiving a data segment in response to the other request, and when memory space available in the queue does not enable the received data segment to be stored: selecting a stream having at least one data segment stored in the queue and for which the associated credit is the smallest; and deleting from the queue a data segment belonging to the selected stream.

Suggesting a route based on desired amount of driver interaction

Abstract: Aspects of the disclosure relate generally to generating and providing route options for an autonomous vehicle. For example, a user may identify a destination, and in response the vehicle's computer may provide routing options to the user. The routing options may be based on typical navigating considerations such as the total travel time, travel distance, fuel economy, etc. Each routing option may include not only an estimated total time, but also information regarding whether and which portions of the route may be maneuvered under the control of the vehicle alone (fully autonomous), a combination of the vehicle and the driver (semiautonomous), or the driver alone. The time of the longest stretch of driving associated with the autonomous mode as well as map information indicating portions of the routes associated with the type of maneuvering control may also be provided.